Vehicle shear mounts are used extensively in body on frame vehicles. Most commonly they are used in trucks and sport utility vehicles to isolate the vertical vibration transmitted from the frame to the body as well as to provide good lateral shake control. A shear mount is located between the body and the frame of the vehicle to provide isolation of lateral and vertical forces. A shear mount or upper mount and a body mount work in conjunction with each other to isolate vertical forces and both are used to improve vehicle ride and handling characteristics. The shear mount or upper mount provides an additional mechanical vibration isolation function for lateral shake control. Depending on the size of the vehicle, there are as many as six combination body and shear mounts used in pairs on opposite sides of the frame.
A typical body or shear mount system is made up of two isolation assemblies: an upper mount and a lower mount. The frame is sandwiched between the upper and lower mount and the vehicle body rests on top of the upper mount. A fastener connects the body to the lower mount, and with further insertion, the fastener attaches the body to the frame sometimes in conjunction with a cage nut. As the frame moves up and down, it vertically pushes against the upper and lower mounts and as the frame moves side to side, it laterally pushes against the upper mount. Vertical stiffness determines the ride control characteristics of a vehicle while lateral stiffness determines the control of the vehicle.
As stated previously, the upper mount or shear mount is typically designed to provide an additional function, namely lateral shake control. Traditionally, solid rubber has been used as a vibration isolation material in designing shear mounts. However, a solid rubber shear mount has several inherent design limitations. First, the design employs three mechanical components. Next, its performance characteristics are limited by the inherent properties of rubber which are excellent in the compressive mode but weak in shear or lateral mode. Finally, a traditional design upper mount utilizes a shear cap component which by design limits the response of the shear mount to compressive forces only. The rubber member in the shear mount portion of the design must be of a relatively high durometer value or hardness to provide sufficient lateral stiffness. However, a high durometer rubber material does not lend itself to good ride and handling characteristics because high durometer rubber material results in high vertical stiffness. Thus, the rubber shear mount inherently has a low lateral rate to vertical rate response ratio. This especially negatively impacts the operator""s response to a vehicle""s drive characteristics subjected to high vertical and lateral shake conditions such as in the case of sport utility vehicles. Additionally, the rubber shear mount lacks sufficient elastomeric properties for good isolation of the vibration transmitted from the frame to the body and is unable to provide good lateral shake control desired for sport utility vehicles.
The present invention provides a body mount for absorbing lateral and vertical vibration from the frame to the body in a vehicle. The shear mount includes an isolator with a base portion, a top portion and a passageway extending from the base portion to the top portion. An insert is located adjacent to the base portion. The insert has a flanged portion and a cylindrical portion extending from the flanged portion. The flanged portion of the insert is encapsulated by overmolding with the cross-linked elastomeric material of the isolator. The isolator and the insert form a one-piece member. A retainer member is located adjacent to the top portion of the isolator. The retainer has a radial portion and an axially extending portion through the passageway in this isolator.
The object of the present invention is to provide a mount which provides both good lateral and vertical stiffness.
Still another object is to provide a mount that is less complex, less expensive to manufacture and weighs less than current known mounts of similar design.
These and other objects and features of the invention will become apparent from the description and especially taken in conjunction with the accompanying drawings illustrating the invention and one embodiment.